1. Field of the Invention
The present invention relates to a novel thiol (meth)acrylate, a resin formed from this (meth)acrylate and a high-refractive-index plastic lens composed of this resin.
2. Description of the Related Art
Olefinic thermosetting resins generally have an excellent heat resistance and chemical resistance, and especially, a resin composed of diallyl phthalate is widely used on an industrial scale because of its excellent heat resistance and chemical resistance and good dimensional stability. In some application fields, higher dimensional stability or chemical resistance and reduced water-absorbing characteristics, however, are required.
Diethylene glycol bisallyl carbonate is often applied to optical uses. However, the diethylene glycol bisally carbonate used for optical articles has a problem in that the refractive index is low.
For eliminating this disadvantage, there have been proposed thiol (meth)acrylates, for example, resins composed mainly of an aromatic thiol ester (Japanese Unexamined Patent Publication No. 63-316766), and an aliphatic thiol ester (U.S. Pat. No. 4,810,812) and Japanese Unexamined Patent Publication No. 63-188660).
Resins proposed in Japanese Unexamined Patent Publication No. 63-316766, U.S. Pat. No. 4,810,812, and Japanese Unexamined Patent Publication No. 63-188660 still have a problem in that optical characteristics having a good balance between a high refractive index and a large Abbe number cannot be obtained. Furthermore, these resins emit a strong offensive smell at the time of processing such as cutting or polishing. Moreover, since these resins are solid at normal temperature, cast polymerization cannot be performed at normal temperature, and the resins have a poor hardness and heat resistance.